The present invention relates to a pneumatic radial tire for passenger cars.
When passenger car tires are rotating at high speed, a centrifugal force is exerted upon the tread portion and in a radial tire the belt will experience "lifting" tending to result in its separation from adjacent rubber compounds. In order to prevent this problem, conventional passenger car tires are provided with reinforcement layers made of organic fiber cords and which are wrapped around the tire in a position radially outward of the belt. The belt is usually made of a plurality of parallel steel cords which are in turn each made up of a plurality of fine steel wires.
Since these organic fiber reinforcement layers are wrapped radially outward of the steel belt, a joint is formed where adjacent turns of reinforcement layers overlap each other. Another joint is formed where the ends of the tread in the form of a single layer are connected. These two joints have been a factor that causes adverse effects on the uniformity of tires.
In response to the need for improved high speed performance of vehicles, there has been a growing demand for a better uniformity of tires. Conventionally, the maximum value of variations in the radial force component of tire (RFV, or radial force variation) has been the principal criterion for defining and characterizing tire uniformity, as well as for describing and evaluating the uniformity characteristics. However, cases have increased in number that defy explanation of the vibratory disturbances or vibrations during high-speed running solely in terms of RFV and it has now become clear that vibrations that occur during high-speed running are more closely correlated to the maximum value of variations in the tractive force component of a tire (TFV, or tractive force variation) rather than RFV. This has led to the recognition that reducing the TFV accompanying high-speed running should be more effective in solving the problem of vibratory disturbances.
U.S. Pat. No. 4,865,102 to Saneto only teaches that the joint areas of the reinforcement layers are spaced 180 degrees apart with respect to the central tire axis. Japanese Patent No. 62-279104 only teaches that the joint area of the tread layers are spaced 180 degrees apart with respect to the central tire axis. Both of the references teach and suggest the relationship of the two joint areas of the tire forming members.